Brain – Human Brain Diagrams and Detailed Information Brain Cortices Full Brain Description [Continued from above] . . . in the study of the body; doctors, psychologists, and scientists are continually endeavoring to learn exactly how the many structures of the brain work together intricately to create our powerful human mind. Anatomy of the Brain There are different ways of dividing the brain anatomically into regions. Let’s use a common method and divide the brain into three main regions based on embryonic development: the forebrain, midbrain and hindbrain. Under these divisions: The forebrain (or prosencephalon) is made up of our incredible cerebrum, thalamus, hypothalamus and pineal gland among other features. Neuroanatomists call the cerebral area the telencephalon and use the term diencephalon (or interbrain) to refer to the area where our thalamus, hypothalamus and pineal gland reside. The midbrain (or mesencephalon), located near the very center of the brain between the interbrain and the hindbrain, is composed of a portion of the brainstem.

The hindbrain (or rhombencephalon) consists of the remaining brainstem as well as our cerebellum and pons. Neuroanatomists have a word to describe the brainstem sub-region of our hindbrain, calling it the myelencephalon, while they use the word metencephalon in reference to our cerebellum and pons collectively. Before exploring these different regions of the brain, first let’s define the important types of cells and tissues that are the building blocks of them all. Histology Brain cells can be broken into two groups: neurons and neuroglia. Neurons, or nerve cells, are the cells that perform all of the communication and processing within the brain. Sensory neurons entering the brain from the peripheral nervous system deliver information about the condition of the body and its surroundings. Most of the neurons in the brain’s gray matter are interneurons, which are responsible for integrating and processing information delivered to the brain by sensory neurons. Interneurons send signals to motor neurons, which carry signals to muscles and glands. Neuroglia, or glial cells, act as the helper cells of the brain; they support and protect the neurons.

In the brain there are four types of glial cells: astrocytes, oligodendrocytes, microglia, and ependymal cells. Astrocytes protect neurons by filtering nutrients out of the blood and preventing chemicals and pathogens from leaving the capillaries of the brain. Oligodendrocytes wrap the axons of neurons in the brain to produce the insulation known as myelin. Myelinated axons transmit nerve signals much faster than unmyelinated axons, so oligodendrocytes accelerate the communication speed of the brain. Microglia act much like white blood cells by attacking and destroying pathogens that invade the brain. Ependymal cells line the capillaries of the choroid plexuses and filter blood plasma to produce cerebrospinal fluid. The tissue of the brain can be broken down into two major classes: gray matter and white matter. Gray matter is made of mostly unmyelinated neurons, most of which are interneurons. The gray matter regions are the areas of nerve connections and processing. White matter is made of mostly myelinated neurons that connect the regions of gray matter to each other and to the rest of the body.

Myelinated neurons transmit nerve signals much faster than unmyelinated axons do. The white matter acts as the information highway of the brain to speed the connections between distant parts of the brain and body. Now let’s begin exploring the main structures of our awesome human brain. HINDBRAIN (RHOMBENCEPHALON) Brainstem Connecting the brain to the spinal cord, the brainstem is the most inferior portion of our brain. Many of the most basic survival functions of the brain are controlled by the brainstem. The brainstem is made of three regions: the medulla oblongata, the pons, and the midbrain. A net-like structure of mixed gray and white matter known as the reticular formation is found in all three regions of the brainstem. The reticular formation controls muscle tone in the body and acts as the switch between consciousness and sleep in the brain. The medulla oblongata is a roughly cylindrical mass of nervous tissue that connects to the spinal cord on its inferior border and to the pons on its superior border. The medulla contains mostly white matter that carries nerve signals ascending into the brain and descending into the spinal cord.

Within the medulla are several regions of gray matter that process involuntary body functions related to homeostasis. The cardiovascular center of the medulla monitors blood pressure and oxygen levels and regulates heart rate to provide sufficient oxygen supplies to the body’s tissues. The medullary rhythmicity center controls the rate of breathing to provide oxygen to the body. Vomiting, sneezing, coughing, and swallowing reflexes are coordinated in this region of the brain as well. The pons is the region of the brainstem found superior to the medulla oblongata, inferior to the midbrain, and anterior to the cerebellum. Together with the cerebellum, it forms what is called the metencephalon. About an inch long and somewhat larger and wider than the medulla, the pons acts as the bridge for nerve signals traveling to and from the cerebellum and carries signals between the superior regions of the brain and the medulla and spinal cord. Cerebellum The cerebellum is a wrinkled, hemispherical region of the brain located posterior to the brainstem and inferior to the cerebrum.

The outer layer of the cerebellum, known as the cerebellar cortex, is made of tightly folded gray matter that provides the processing power of the cerebellum. Deep to the cerebellar cortex is a tree-shaped layer of white matter called the arbor vitae, which means ‘tree of life’. The arbor vitae connects the processing regions of cerebellar cortex to the rest of the brain and body. The cerebellum helps to control motor functions such as balance, posture, and coordination of complex muscle activities. The cerebellum receives sensory inputs from the muscles and joints of the body and uses this information to keep the body balanced and to maintain posture. The cerebellum also controls the timing and finesse of complex motor actions such as walking, writing, and speech. MIDBRAIN (MESENCEPHALON) The midbrain, also known as the mesencephalon, is the most superior region of the brainstem. Found between the pons and the diencephalon, the midbrain can be further subdivided into 2 main regions: the tectum and the cerebral peduncles.

The tectum is the posterior region of the midbrain, containing relays for reflexes that involve auditory and visual information. The pupillary reflex (adjustment for light intensity), accommodation reflex (focus on near or far away objects), and startle reflexes are among the many reflexes relayed through this region. Forming the anterior region of the midbrain, the cerebral peduncles contain many nerve tracts and the substantia nigra. Nerve tracts passing through the cerebral peduncles connect regions of the cerebrum and thalamus to the spinal cord and lower regions of the brainstem. The substantia nigra is a region of dark melanin-containing neurons that is involved in the inhibition of movement. Degeneration of the substantia nigra leads to a loss of motor control known as Parkinson’s disease. FOREBRAIN (PROSENCEPHALON) Diencephalon Superior and anterior to the midbrain is the region known as the interbrain, or diencephalon. The thalamus, hypothalamus, and pineal glands make up the major regions of the diencephalon.

The thalamus consists of a pair of oval masses of gray matter inferior to the lateral ventricles and surrounding the third ventricle. Sensory neurons entering the brain from the peripheral nervous system form relays with neurons in the thalamus that continue on to the cerebral cortex. In this way the thalamus acts like the switchboard operator of the brain by routing sensory inputs to the correct regions of the cerebral cortex. The thalamus has an important role in learning by routing sensory information into processing and memory centers of the cerebrum. The hypothalamus is a region of the brain located inferior to the thalamus and superior to the pituitary gland. The hypothalamus acts as the brain’s control center for body temperature, hunger, thirst, blood pressure, heart rate, and the production of hormones. In response to changes in the condition of the body detected by sensory receptors, the hypothalamus sends signals to glands, smooth muscles, and the heart to counteract these changes. For example, in response to increases in body temperature, the hypothalamus stimulates the secretion of sweat by sweat glands in the skin.

The hypothalamus also sends signals to the cerebral cortex to produce the feelings of hunger and thirst when the body is lacking food or water. These signals stimulate the conscious mind to seek out food or water to correct this situation. The hypothalamus also directly controls the pituitary gland by producing hormones. Some of these hormones, such as oxytocin and antidiuretic hormone, are produced in the hypothalamus and stored in the posterior pituitary gland. Other hormones, such as releasing and inhibiting hormones, are secreted into the blood to stimulate or inhibit hormone production in the anterior pituitary gland. The pineal gland is a small gland located posterior to the thalamus in a sub-region called the epithalamus. The pineal gland produces the hormone melatonin. Light striking the retina of the eyes sends signals to inhibit the function of the pineal gland. In the dark, the pineal gland secretes melatonin, which has a sedative effect on the brain and helps to induce sleep. This function of the pineal gland helps to explain why darkness is sleep-inducing and light tends to disturb sleep. Babies produce large amounts of melatonin, allowing them to sleep as long as 16 hours per day.

The pineal gland produces less melatonin as people age, resulting in difficulty sleeping during adulthood. Cerebrum The largest region of the human brain, our cerebrum controls higher brain functions such as language, logic, reasoning, and creativity. The cerebrum surrounds the diencephalon and is located superior to the cerebellum and brainstem. A deep furrow known as the longitudinal fissure runs midsagittally down the center of the cerebrum, dividing the cerebrum into the left and right hemispheres. Each hemisphere can be further divided into 4 lobes: frontal, parietal, temporal, and occipital. The lobes are named for the skull bones that cover them. The surface of the cerebrum is a convoluted layer of gray matter known as the cerebral cortex. Most of the processing of the cerebrum takes place within the cerebral cortex. The bulges of cortex are called gyri (singular: gyrus) while the indentations are called sulci (singular: sulcus). Deep to the cerebral cortex is a layer of cerebral white matter.

White matter contains the connections between the regions of the cerebrum as well as between the cerebrum and the rest of the body. A band of white matter called the corpus callosum connects the left and right hemispheres of the cerebrum and allows the hemispheres to communicate with each other. Deep within the cerebral white matter are several regions of gray matter that make up the basal nuclei and the limbic system. The basal nuclei, including the globus pallidus, striatum, and subthalamic nucleus, work together with the substantia nigra of the midbrain to regulate and control muscle movements. Specifically, these regions help to control muscle tone, posture, and subconscious skeletal muscle. The limbic system is another group of deep gray matter regions, including the hippocampus and amygdala, which are involved in memory, survival, and emotions. The limbic system helps the body to react to emergency and highly emotional situations with fast, almost involuntary actions. With so many vital functions under the control of a single incredible organ - and so many important functions carried out in its outer layers - how does our body protect the brain from damage?

Our skull clearly offers quite a bit of protection, but what protects the brain from the skull itself? Read on! Meninges Three layers of tissue, collectively known as the meninges, surround and protect the brain and spinal cord. The dura mater forms the leathery, outermost layer of the meninges. Dense irregular connective tissue made of tough collagen fibers gives the dura mater its strength. The dura mater forms a pocket around the brain and spinal cord to hold the cerebrospinal fluid and prevent mechanical damage to the soft nervous tissue. The name dura mater comes from the Latin for “tough mother,” due to its protective nature. The arachnoid mater is found lining the inside of the dura mater. Much thinner and more delicate than the dura mater, it contains many thin fibers that connect the dura mater and pia mater. The name arachnoid mater comes from the Latin for “spider-like mother”, as its fibers resemble a spider web. Beneath the arachnoid mater is a fluid-filled region known as the subarachnoid space.

As the innermost of the meningeal layers, the pia mater rests directly on the surface of the brain and spinal cord. The pia mater’s many blood vessels provide nutrients and oxygen to the nervous tissue of the brain. The pia mater also helps to regulate the flow of materials from the bloodstream and cerebrospinal fluid into nervous tissue. Cerebrospinal Fluid Cerebrospinal fluid (CSF) – a clear fluid that surrounds the brain and spinal cord – provides many important functions to the central nervous system. Rather than being firmly anchored to their surrounding bones, the brain and spinal cord float within the CSF. CSF fills the subarachnoid space and exerts pressure on the outside of the brain and spinal cord. The pressure of the CSF acts as a stabilizer and shock absorber for the brain and spinal cord as they float within the hollow spaces of the skull and vertebrae. Inside of the brain, small CSF-filled cavities called ventricles expand under the pressure of CSF to lift and inflate the soft brain tissue. Cerebrospinal fluid is produced in the brain by capillaries lined with ependymal cells known as choroid plexuses.

Blood plasma passing through the capillaries is filtered by the ependymal cells and released into the subarachnoid space as CSF. The CSF contains glucose, oxygen, and ions, which it helps to distribute throughout the nervous tissue. CSF also transports waste products away from nervous tissues. After circulating around the brain and spinal cord, CSF enters small structures known as arachnoid villi where it is reabsorbed into the bloodstream. Arachnoid villi are finger-like extensions of the arachnoid mater that pass through the dura mater and into the superior sagittal sinus. The superior sagittal sinus is a vein that runs through the longitudinal fissure of the brain and carries blood and cerebrospinal fluid from the brain back to the heart. Physiology of the Brain Metabolism Despite weighing only about 3 pounds, the brain consumes as much as 20% of the oxygen and glucose taken in by the body. Nervous tissue in the brain has a very high metabolic rate due to the sheer number of decisions and processes taking place within the brain at any given time. Large volumes of blood must be constantly delivered to the brain in order to maintain proper brain function.

Any interruption in the delivery of blood to the brain leads very quickly to dizziness, disorientation, and eventually unconsciousness. Sensory The brain receives information about the body’s condition and surroundings from all of the sensory receptors in the body. All of this information is fed into sensory areas of the brain, which put this information together to create a perception of the body’s internal and external conditions. Some of this sensory information is autonomic sensory information that tells the brain subconsciously about the condition of the body. Body temperature, heart rate, and blood pressure are all autonomic senses that the body receives. Other information is somatic sensory information that the brain is consciously aware of. Touch, sight, sound, and hearing are all examples of somatic senses. Motor Control Our brain directly controls almost all movement in the body. A region of the cerebral cortex known as the motor area sends signals to the skeletal muscles to produce all voluntary movements. The basal nuclei of the cerebrum and gray matter in the brainstem help to control these movements subconsciously and prevent extraneous motions that are undesired. The cerebellum helps with the timing and coordination of these movements during complex motions.

Finally, smooth muscle tissue, cardiac muscle tissue, and glands are stimulated by motor outputs of the autonomic regions of the brain. Processing Once sensory information has entered the brain, the association areas of the brain go to work processing and analyzing this information. Sensory information is combined, evaluated, and compared to prior experiences, providing the brain with an accurate picture of its conditions. The association areas also work to develop plans of action that are sent to the brain’s motor regions in order to produce a change in the body through muscles or glands. Association areas also work to create our thoughts, plans, and personality. Learning and Memory The brain needs to store many different types of information that it receives from the senses and that it develops through thinking in the association areas. Information in the brain is stored in a few different ways depending on its source and how long it is needed. Our brain maintains short-term memory to keep track of the tasks in which the brain is currently engaged. Short-term memory is believed to consist of a group of neurons that stimulate each other in a loop to keep data in the brain’s memory. New information replaces the old information in short-term memory within a few seconds or minutes, unless the information gets moved to long-term memory.

Long-term memory is stored in the brain by the hippocampus. The hippocampus transfers information from short-term memory to memory-storage regions of the brain, particularly in the cerebral cortex of the temporal lobes. Memory related to motor skills (known as procedural memory) is stored by the cerebellum and basal nuclei. Homeostasis The brain acts as the body’s control center by maintaining the homeostasis of many diverse functions such as breathing, heart rate, body temperature, and hunger. The brainstem and the hypothalamus are the brain structures most concerned with homeostasis. In the brainstem, the medulla oblongata contains the cardiovascular center that monitors the levels of dissolved carbon dioxide and oxygen in the blood, along with blood pressure. The cardiovascular center adjusts the heart rate and blood vessel dilation to maintain healthy levels of dissolved gases in the blood and to maintain a healthy blood pressure. The medullary rhythmicity center of the medulla monitors oxygen and carbon dioxide levels in the blood and adjusts the rate of breathing to keep these levels in balance. The hypothalamus controls the homeostasis of body temperature, blood pressure, sleep, thirst, and hunger. Many autonomic sensory receptors for temperature, pressure, and chemicals feed into the hypothalamus.

The hypothalamus processes the sensory information that it receives and sends the output to autonomic effectors in the body such as sweat glands, the heart, and the kidneys. Sleep While sleep may seem to be a time of rest for the brain, this organ is actually extremely active during sleep. The hypothalamus maintains the body’s 24 hour biological clock, known as the circadian clock. When the circadian clock indicates that the time for sleep has arrived, it sends signals to the reticular activating system of the brainstem to reduce its stimulation of the cerebral cortex. Reduction in the stimulation of the cerebral cortex leads to a sense of sleepiness and eventually leads to sleep. In a state of sleep, the brain stops maintaining consciousness, reduces some of its sensitivity to sensory input, relaxes skeletal muscles, and completes many administrative functions. These administrative functions include the consolidation and storage of memory, dreaming, and development of nervous tissue. There are two main stages of sleep: rapid eye movement (REM) and non-rapid eye movement (NREM). During REM sleep, the body becomes paralyzed while the eyes move back and forth quickly. Dreaming is common during REM sleep and it is believed that some memories are stored during this phase.

NREM sleep is a period of slow eye movement or no eye movement, culminating in a deep sleep of low brain electrical activity. Dreaming during NREM sleep is rare, but memories are still processed and stored during this time. Reflexes A reflex is a fast, involuntary reaction to a form of internal or external stimulus. Many reflexes in the body are integrated in the brain, including the pupillary light reflex, coughing, and sneezing. Many reflexes protect the body from harm. For instance, coughing and sneezing clear the airways of the lungs. Other reflexes help the body respond to stimuli, such as adjusting the pupils to bright or dim light. All reflexes happen quickly by bypassing the control centers of the cerebral cortex and integrating in the lower regions of the brain such as the midbrain or limbic system. Prepared by Tim Taylor, Anatomy and Physiology Instructor Brain Anatomy | White Matter, Cerebellum, Cerebral Cortex, Medulla limbic system reticular activating system The brain can be divided into two major parts: the lower brain stem and the higher forebrain. The brain stem sits above the spinal cord and has many connections between them.

The brain stem, the most primitive part of the brain, is made up of the medulla, pons, cerebellum, midbrain, hypothalamus and thalamus. The cerebral cortex, limbic system and basal ganglia make up the forebrain. The forebrain deals with homeostasis, emotions and conscious actions. The brain’s outer layer is only 1/4 inch thick but if flattened out would cover the size of an office desk. It has about 50 billion nerve cells. The cerebrum is the largest part of the brain and is part of the forebrain. It houses the nerve center that controls sensory, motor activities and intelligence. The outer layer, the cerebral cortex, is made of nerve fibers called gray matter. The inner layer is made of a different type of nerve fibers called white matter. The basal ganglia is found in the white matter. The cerebrum is divided in to left and right hemispheres. The left half controls the right side of the body and the right half controls the left side of the body. A mass of nerve fibers known as the corpus callosum connects the two hemispheres and allows communication between the two.

The surface of the cerebrum is made up of gyri and sulci. A cortex is the outer layer of any organ. The cerebral cortex is the outer layer of the brain, called gray matter. It is where our conscious thoughts and actions take place. Many of the signals our brain receives from our senses are registered in the cerebral cortex. The visual cortex is in the lower back part of the brain and is where our brain registers what we see. The somatosensory cortex is a band that runs over the top of the brain is where our brain registers a touch on any part of our body. The motor cortex is just in front of the somatosensory cortex and it sends out signals to muscles to make them move. The more nerve endings a part of the body has, the more of the sensory cortex it occupies. A big portion of the sensory cortex is taken up by our lips and face. Our hands take up almost as much as our face and our feet almost as much as our hands. This is because we move our hands and lips all the time and both are very sensitive. The cerebellum, “little brain”, is the second largest region of the brain.

It is located behind and below the cerebrum and at the back of the brain stem and attached to the midbrain. It has two hemispheres and an outer cortex of gray matter and an inner core of white matter. The cerebellum is involved in movement and coordination, walking, posture, reflexes, eye and head movement. It coordinates subconscious movements such as balance and coordinated movement. The cerebellum is constantly receiving updates about the body’s position and movement. It also sends instructions to our muscles that adjust our posture and keep our body moving smoothly. The diencephalon is located between the cerebrum and midbrain. It consists of the thalamus and hypothalamus which lie deep in the cerebral hemispheres. Centers in the hypothalamus regulate our body temperature, blood sugar, hunger and hormones. The thalamus is involved with sensory signals sent to the higher forebrain, in particular the cerebral cortex. The thalamus also participates in motor control and regulating cortex excitement. Several pathways connect the brainstem to the lower motor centers in the spinal cord and the higher ones in the forebrain. The brain is the control center of the body and contains billions of nerve cells.

The brain stem lies just below the cerebrum and in front of the cerebellum. It continues from the cerebrum above and connects to the spinal cord below. The brain stem is made up of the midbrain, pons and medulla oblongata. It carries out many vital functions of the body for maintenance and survival such as breathing, heartbeat, and blood pressure. It also controls vomiting, coughing, sneezing and swallowing. It is the body’s “autopilot.” It also provides pathways for nerve fibers between the higher and lower neural centers. It is also the origin for 10 of the 12 cranial nerves. The 12 cranial nerves enter the brain directly and are not connected to the spinal cord. The midbrain is the reflex center for cranial nerves III and IV and is involved in eye reflexes and movements. The pons helps regular breathing. It connects the cerebellum with the cerebrum and links the midbrain to the medulla oblongata. The pons is the reflex center for cranial nerves V through VIII. The pons is involved in chewing, taste, saliva, hearing and equilibrium.

The medulla oblongata joins the spinal cord at the foramen magnum. It influences heart, breathing and circulation. It’s the center for vomiting, coughing and hiccuping. The medulla—the most primitive brain structure—controls our digestive, respiratory and circulatory systems. The ponsinteracts with the cerebellum, motor control and respiration. Other structures in the pons control sleep and excitement. The pons also relays information between the brain and the spinal cord. The basal ganglia is found in the forebrain and consist of structures involved in motor processes. The basal ganglia works along with the motor areas of the cortex and cerebellum for planning and coordinating certain voluntary movements. The basal ganglia is made of gray matter. The limbic system, or limbic lobe, is involved in the expression of intimate behaviors and emotions, hunger, aggression. The limbic system also screens all sensory messages to the cerebral cortex. It is located deep in the temporal lobe. The limbic system includes these structures: cingulate gyrus, corpus callosum, mammillary body, olfactory tract, amygdala, and hippocampus.

The hypothalamus affects body temperature, appetite, water balance, pituitary secretions, emotions, and autonomic functions including cycles of waking and sleeping. Even though many functions of the brain are very localized to certain areas and parts of the brain, these parts work together as a whole—particularly in learning, memory, and consciousness. Ventricles are fluid filled cavities in the brain; there are four of them. The ventricles connect with each other and produce cerebrospinal fluid which is a clear, shock-absorbing liquid that is constantly moving. The cerebrospinal fluid cushions the brain, distributes nutrients and collects wastes. Blood Vessels in the Brain The oxygen supply for the brain comes from 4 major arteries, two vertebral arteries and two carotid arteries . The two vertebral arteries supply blood to the back of the brain. The two carotid arteries branch and supply oxygen to the front and middle of the brain. The front and back arteries interconnect at the circle of Willis at the base of the brain. The circle of Willis ensures a continuous blood supply to the brain.

Cross Section Images of the Brain Sectioning the Brain Left and Right Hemispheres The forebrain consists of two almost symmetrical cerebral hemispheres made up of the cerebral cortex, the basal ganglia and the limbic system. The two hemispheres are divided by the longitudinal cerebral fissure and connected by a massive bundle of fibers called the corpus callosum. The surface of the two hemispheres is covered by a large, but thin layer of nerve cells called gray matter. Because of the area size of the gray matter, fitting it into the skull causes folds. The grooves in these folds are called sulci (singular sulcus), the ridges are called gyri (singular gyrus). The deeper grooves are called fissures. The cortex is a large mass of nerve fibers called white matter. These nerve fibers are highly developed and able to analyze both motor and sensory information. The left and right hemispheres may look the same, but each side functions differently. Speech and language, reasoning and analysis, and certain communications are on the left side for most people. The left side of the brain sends and receives information to the right side of the body including the right hand.

The right hemisphere is concerned with sensory input, auditory and visual awareness, creative abilities, and spatial-temporal awareness—that is what is happening around us moment by moment. The right brain controls the left side of the body. Each of the cerebral hemispheres is divided into four lobes and are name for the cranial (skull) bones that lie over them: The frontal lobe extends from the tip of the front of the hemisphere to the central sulcus. The back areas of the frontal lobe specialize in motor functions, including language and voluntary movement; the front areas are involved in learning, planning and other higher psychological processes like our personality and behavior. The occipital lobe is at the back of the hemisphere and is involved in interpreting visual stimuli, that is, what we see. The parietal lobes are at the top and outside areas between the occipital lobe and the frontal lobe and is involved in sensory functions of the skin including pain, temperature, and touch. It also interprets size, shape, distance, vibrations and texture. Other areas are also important in cognitive and intellectual processes. The temporal lobe controls the hearing centers, language comprehension, storing and recalling memories and related areas including some speech centers.

Other areas of the brain also affect memory. The front and bottom areas of the temporal lobe are involved in smell and functions of the limbic system. Brain Structures and Their Functions Brain Structures and their Functions Brain Stem The nervous system is your body's decision and communication center. The central nervous system (CNS) is made of the brain and the spinal cord and the peripheral nervous system (PNS) is made of nerves. Together they control every part of your daily life, from breathing and blinking to helping you memorize facts for a test. Nerves reach from your brain to your face, ears, eyes, nose, and spinal cord... and from the spinal cord to the rest of your body. Sensory nerves gather information from the environment, send that info to the spinal cord, which then speed the message to the brain. The brain then makes sense of that message and fires off a response. Motor neurons deliver the instructions from the brain to the rest of your body. The spinal cord, made of a bundle of nerves running up and down the spine, is similar to a superhighway, speeding messages to and from the brain at every second. The brain is made of three main parts: the forebrain, midbrain, and hindbrain.

The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla. Often the midbrain, pons, and medulla are referred to together as the brainstem. The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. Here is a visual representation of the cortex: What do each of these lobes do? Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli Occipital Lobe- associated with visual processing Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech Note that the cerebral cortex is highly wrinkled.

Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it. We will discuss the relevance of the degree of cortical folding (or gyrencephalization) later. (Go here for more information about cortical folding) A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. Sometimes the right hemisphere is associated with creativity and the left hemispheres is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres. Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibers underneath carry signals between the nerve cells and other parts of the brain and body. The neocortex occupies the bulk of the cerebrum. This is a six-layered structure of the cerebral cortex which is only found in mammals. It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc).

For more information about the neocortex, click here . The Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance. The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals which scientists assume to have evolved prior to humans, for example reptiles, do have developed cerebellums. However, reptiles do not have neocortex. Go here for more discussion of the neocortex or go to the following web site for a more detailed look at evolution of brain structures and intelligence: "Ask the Experts": Evolution and Intelligence Limbic System: The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum. Like the cerebellum, evolutionarily the structure is rather old. This system contains the thalamus, hypothalamus, amygdala, and hippocampus.

Here is a visual representation of this system, from a midsagittal view of the human brain: Click on the words to learn what these structures do: Brain Anatomy: Overview, Gross Anatomy: Cerebrum, Gross Anatomy: Cortex Brain Anatomy Author: Anand I Rughani, MD; Chief Editor: Thomas R Gest, PhD more... Share Overview Overview The central nervous system consists of the brain and the spinal cord. The peripheral nervous system consists of the extensions of neural structures beyond the central nervous system and includes somatic and autonomic divisions. The brain is composed of 3 main structural divisions: the cerebrum, the brainstem, and the cerebellum (see the images below). At the base of the brain is the brainstem, which extends from the upper cervical spinal cord to the diencephalon of the cerebrum. The brainstem is divided into the medulla, pons, and midbrain. Posterior to the brainstem lies the cerebellum. Brain, coronal view. Next: Gross Anatomy: Cerebrum The cerebrum is the largest component of the brain. It is divided into right and left hemispheres.

The corpus callosum is the collection of white matter fibers that joins these hemispheres. Each of the cerebral hemispheres is further divided into 4 lobes: the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe. The medial temporal lobe structures are considered by some to be part of the so-called limbic lobe. Briefly, the frontal lobe is distinguished from the parietal lobe posteriorly by the central sulcus (see the image below). The frontal lobe and parietal lobes are divided inferiorly from the temporal lobe by the lateral sulcus. The parietal lobe is distinguished from the occipital lobe by the parieto-occipital sulcus on the medial surface. Lateral and medial surfaces of cerebrum, showing major sulci and gyri. View Media Gallery The cerebrum is further divided into the telencephalon and diencephalon. The telencephalon consists of the cortex, the subcortical fibers, and the basal nuclei. The diencephalon mainly consists of the thalamus and hypothalamus.

The telencephalon of the cerebrum is disproportionately well-developed in humans as compared with other mammals. Cortex and subcortical fibers The outermost layer of the cerebrum is the cortex, which has a slightly gray appearance--hence the term "gray matter." The cortex has a folded structure; each fold is termed a gyrus, while each groove between the folds is termed a sulcus. Cortical anatomy is discussed in greater detail below. Below the cortex are axons, which are long fibers that emanate from and connect neurons. Axons are insulated by myelin, which increases the speed of conduction. Myelin is what gives the white appearance to these fibers of the brain--hence the term "white matter." Limbic system The limbic system is a grouping of cortical and subcortical structures involved in memory formation and emotional responses. The limbic system allows for complex interactions between the cortex, the thalamus, the hypothalamus, and the brainstem. The limbic system is not defined by strict anatomic boundaries but incorporates several important structures.

The limbic structures conventionally include the amygdala, the hippocampus, the fornix, the mammillary bodies, the cingulate gyrus, and the parahippocampal gyrus. The functional connections within the limbic system are best summarized by the Papez circuit. From the hippocampus, signals are relayed via the fornix to the mammillary bodies and via the mammillothalamic tract to the anterior nucleus of the thalamus. The thalamocingulate radiation then projects to the cingulate gyrus and back to the hippocampus to complete the circuit. The hippocampus serves as a primary output structure of the limbic system. Unlike the 6-layered neocortex, the hippocampus only has 3 layers and is termed the archicortex. The hippocampus is felt to be a structure that is crucial to formation of memory--more specifically, a type of memory called declarative or explicit memory. Declarative memory is essentially the ability to recall life events of the past such as what meal was eaten for breakfast or where the car is parked. Over time, however, certain declarative memories from the distant past can be independently recalled without the hippocampal structures.

The hippocampus likely allows long-term memory encoding in the cortex and allows short-term memory retrieval. In laboratory studies of animals and humans, the hippocampus has been shown to also have a cellular memory termed "long-term potentiation." The amygdala is a collection of nuclei that lies within the uncus. It receives multiple modes of sensory information as inputs. The outputs from the amygdala travel through the stria terminalis and the ventral amygdalofugal pathway. Output structures include the hypothalamus, as well as the thalamus, hippocampus, brainstem, and cortex. The amygdala appears to be involved in mediating the emotional aspects of memory, especially the subjective aspects of fear responses. Basal nuclei (ganglia) The basal nuclei (formerly referred to as the basal ganglia) comprise the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. Pairs of these structures bear different names. The putamen and globus pallidus combined form the lentiform nuclei. The putamen and caudate nucleus combined form the striatum. The striatum derives its name from the striped appearance given by the gray matter connections bridging across the internal capsule.

The basal nuclei are closely integrated with the motor cortex, premotor cortex, and motor nuclei of the thalamus and plays a crucial role in modulation of movements. The primary input to the basal nuclei is from the primary motor cortex and premotor cortex (Brodmann areas 4 and 6) and consists primarily of the pyramidal cells in cortical layer V. These excitatory projections lead primarily to the striatum. The striatum also receives input from the dopaminergic cells of the substantia nigra. In turn, the striatum sends inhibitory projections to the globus pallidus externa and interna. The globus pallidus externa sends inhibitory projections to the subthalamic nucleus, which sends excitatory projections to the globus pallidus interna. The globus pallidus interna in turn projects to the ventral anterior and ventral lateral nuclei of the thalamus. Certain movement disorders can be traced to pathologies in the basal nuclei, the most notable being Parkinson disease , which is related to deficiencies of dopaminergic cells of the substantia nigra.

Huntington disease is a heritable disorder that involves degeneration of the striatum and leads to progressive jerky, or choreiform, movement. Thalamus Positioned between the brainstem and the telencephalon, the diencephalon is composed of the thalamus, the epithalamus, the subthalamus, and the hypothalamus. The thalamus serves as a relay station for ascending input to the cortex and receives information from each of the cardinal senses (except smell). It is hypothesized that the thalamus serves a gating function in filtering information. The thalamus consists of multiple nuclei that are briefly described here (see the image below). Major nuclei of thalamus. View Media Gallery Left and right sides of the thalamus are divided by the third ventricle. Each side is then divided by the internal medullary lamina into a series of anterior nuclei, ventrolateral nuclei, and medial nuclei. Smaller nuclei are found within these regions, numbering perhaps in excess of 100. The anterior thalamic nuclei are functionally associated with the limbic system and share reciprocal connections with the cingulate gyrus and the mammillary bodies.

The medial nuclei project to the frontal association cortex and premotor cortex, with reciprocal connectivity. The ventrolateral nuclei can be further divided into the ventral anterior (VA), ventral lateral (VL), ventral posterolateral (VPL), and ventral posteromedial (VPM) nuclei. The VA and VL nuclei share input from the globus pallidus and projections to the motor cortex. The VPL and VPM serve as sensory relays in the body and face, respectively. The lateral nuclei are divided into lateral dorsal and lateral posterior nuclei, with projections to the cingulate gyrus and parietal cortex, respectively. Other thalamic structures not included in the anatomic divisions above include the medial and lateral geniculate bodies, which process auditory and visual information, respectively. The pulvinar connects reciprocally with the parietal and occipital association cortex. Intralaminar nuclei within the internal medullary lamina obtain input from the brainstem, cerebellum, and other thalamic nuclei and project to basal nuclei structures and other thalamic nuclei.

Amongst the intralaminar nuclei, the centromedian nucleus is a part of the reticular activating system, which plays a role in maintaining cortical arousal. Epithalamus The epithalamus is made up of the habenula, the habenular commissure, the posterior commissure, and the pineal gland. Subthalamus Located between the midbrain and the thalamus, the subthalamus contains the subthalamic nucleus, the red nucleus, and the substantia nigra. Subthalamic structures are closely integrated with the basal nuclei and play a role in modulation of movement. Hypothalamus Thy hypothalamic nuclei lie in the walls of the third ventricle anteriorly. The hypothalamus is involved in mediating endocrine, autonomic, visceral, and homeostatic functions. It can roughly be divided into anterior, posterior, and middle groups of nuclei. The anterior nuclei include the preoptic, the supraoptic, and paraventricular nuclei. The posterior nuclei include the supramammillary nucleus, the mammillary nucleus, the intercalate nucleus, and the posterior nucleus.

The middle nuclei include the infundibular, tuberal, dorsomedial, ventromedial, and lateral nuclei. Parasympathetic control can be attributed to the anterior and medial nuclear groups, whereas sympathetic control can be attributed to the posterior and lateral nuclear groups. Satiety can be localized to stimulation of medial nuclei, and hunger can be localized to stimulation of lateral nuclei. Other functions of the hypothalamus include regulation of body temperature, heart rate, blood pressure, and water balance. The hypothalamus has close connections with the cingulate gyrus, frontal lobe, hippocampus, thalamus, brainstem, spinal cord, basal nuclei, and pituitary gland. Previous View Media Gallery Medulla oblongata The medulla oblongata, or simply medulla, is continuous with and superior to the cervical spinal cord. There are several external anatomic features of the medulla that can be visible grossly. Ventrally, the pyramids and pyramidal decussation is visualized just below the pons. These are the descending corticospinal tracts. Just lateral to the pyramids, the rootlets of the hypoglossal nerve can be seen as they exit the brainstem.

Lateral to the rootlets of the hypoglossal nerve is the inferior olive. Dorsolateral to the inferior olive, the rootlets of the 9th and 10th cranial nerves (glossopharyngeal and vagus) exit. Dorsally, 2 pairs of protrusions are visible, which are the gracile tubercles medially and the cuneate tubercles just lateral to those. These represent the nuclei where sensory information from the dorsal columns is relayed onto thalamic projection neurons. Just superior to these protrusions is the floor of the fourth ventricle, which bears several characteristic impressions. The vagal trigone is the dorsal nucleus of the vagus nerve (cranial nerve X) and lies inferiorly, just below the hypoglossal trigone. Pons Superior to the medulla lies the pons, the ventral surface of which has a characteristic band of horizontal fibers. These fibers are the pontocerebellar fibers that are in turn projections from the corticopontine fibers. They cross to enter the contralateral middle cerebellar peduncle and thus enter the cerebellum.

On either side of the midline, there are bulges that are produced by the descending corticospinal tracts. At the pontomedullary junction, the 6th cranial nerve (abducens) can be seen exiting the brainstem. Laterally, but anterior to the middle cerebellar peduncle, the fifth cranial nerve (trigeminal) is seen exiting the brainstem. Below the middle cerebellar peduncle, the seventh and eighth cranial nerves (facial and vestibulocochlear) can be seen exiting. Dorsally, the pons forms the floor of the fourth ventricle. Midbrain The midbrain, also termed the mesencephalon, is the superiormost aspect of the brainstem. Ventrally, the midbrain appears as 2 bundles that diverge rostrally as the cerebral peduncles. Between the cerebral peduncles, the third cranial nerve (oculomotor) can be seen exiting. The fourth cranial nerve (trochlear) exits dorsally and is unique in this regard. It then courses anteriorly against the cerebral peduncles.

The posterior aspect of the midbrain has 2 pairs of characteristic protrusions, the superior and inferior colliculi. The superior colliculi are involved in mediating the vestibulo-ocular reflex, whereas the inferior colliculi are involved in sound localization. Cranial nerves There are 12 pairs of cranial nerves that function mainly to convey motor signals to and sensory information from the head and neck. The lower cranial nerves have somewhat more complex visceral functions that are not strictly limited to the head and neck.

The cranial nerves are as follows: I: The olfactory nerve relays information from the nerves of the olfactory epithelium to mesial temporal lobe and frontal lobe structures II: The optic nerve relays visual information from the retina; the right and left optic nerves then join at the optic chiasm, where they give rise to the optic tracts, which convey visual information to the thalamus and brainstem and, ultimately, the visual cortex; optic gliomas can arise from the optic nerve III: The oculomotor nerve is principally involved in the control of eye movements through its innervation of the superior rectus, the medial rectus, the inferior rectus, and the inferior oblique muscles IV: The trochlear nerve innervates the superior oblique muscle and is purely a motor nerve V: The trigeminal nerve is both a motor and sensory nerve and has 3 divisions, V 1 (the ophthalmic division), V 2 (the maxillary division), and V 3 (the mandibular division); it is involved in conveying sensory information from the face and also in controlling the muscles of mastication; vascular compression of the branches of the trigeminal nerve near its entry into the brainstem

 has been associated with some types of facial pain, including trigeminal neuralgia VI: The abducens nerve innervates the lateral rectus nerve, allowing lateral eye movements VII: The facial nerve is principally involved in innervation of the muscles of facial expression and also plays a role in tearing, salivation, and taste; Bell's palsy is a relatively common facial nerve palsy VIII: The vestibulocochlear nerve is a purely sensory nerve that conveys auditory information from the cochlea to the brainstem via the cochlear branch; the vestibular branch conveys proprioceptive information about head position and movement from the inner ear to the brainstem; acoustic neuromas are typically benign tumors that can arise from the vestibular portion of this nerve IX: The glossopharyngeal nerve is involved in taste and salivation, as well as sensation in the oropharynx; the afferent limb of the gag reflex is mediated by the glossopharyngeal nerve X: The vagus nerve conveys visceral sensation to the brainstem and also controls some visceral functions, such as heart rate and gastrointestinal motility XI: The accessory nerve has contributions from a spinal component and innervates neck muscles involved in head turning XII: The hypog

lossal nerve is a motor nerve that innervates muscles of the tongue Previous View Media Gallery The innermost of the 3 layers is the pia mater, which tightly covers the brain itself, conforming to its grooves and folds.

This layer is rich with blood vessels that descend into the brain. Outside the pia mater, which tightly contours the brain, is the arachnoid mater. The arachnoid mater is a thin weblike layer. Between the pia mater and the arachnoid mater is a space called the subarachnoid space, which contains cerebrospinal fluid (CSF). This space is where the major arteries supplying blood to the brain lie. If a blood vessel ruptures in this space, it can cause a subarachnoid hemorrhage . The arachnoid cap cells can give rise to meningiomas , a usually benign tumor. The outermost meningeal layer is the dura mater, which lines the interior of the skull. The dura mater is composed of 2 individual layers, the meningeal dura and the periosteal dura. For the most part, these layers are fused; venous sinuses can be found in areas of separation. The tentorium cerebelli is a dura mater fold that separates the cerebellum from the cerebrum. The falx cerebri is a fold that separates the left and right cerebral hemispheres.

Between the arachnoid mater and the dura mater is the subdural space. If bleeding occurs in the space underneath the dura mater, it is called a subdural hematoma . If bleeding occurs outside the dura but underneath the skull, this is called an epidural hematoma . Previous View Media Gallery From the fourth ventricle, CSF flows into the subarachnoid space around both the brain and the spinal cord. From the subarachnoid space, CSF is then absorbed into the venous system. Arachnoid granulations or villi are structures projecting into the superior sagittal sinus that release CSF back into the venous system. Hydrocephalus is a condition in which production of CSF is disproportionate to absorption. This is most commonly caused by impaired absorption resulting from obstruction of the CSF circulatory pathways, in which case it is termed obstructive hydrocephalus. This also occurs when the absorption of CSF is impaired, in which case it is termed communicating hydrocephalus. Rarely is hydrocephalus caused by increased CSF production.

Previous View Media Gallery Some of the earliest contributions to modern language mapping can be traced to the work of neurologist Paul Broca, who studied the language deficits in patients with stroke. Broca's area, as it is termed, is a region of the frontal operculum, which also overlaps with Brodmann area 44 and 45. Three overlapping names describe this region, which is responsible for speech production. Selective damage to this region leads to difficulty speaking but typically with preserved comprehension. In contrast, Wernicke's area refers to the posterior aspect of the superior temporal gyrus, which overlaps with Brodmann area 22. This region is generally responsible for speech comprehension, and selective injury to it can lead to impaired understanding with preserved speech production. Additionally, language function is hemispherically dominant. This means that Broca's and Wernicke's aphasia typically result from damage to the hemisphere that is dominant for language. In right-handed individuals, the left hemisphere is nearly always dominant for language. However, among left-handed individuals, the left hemisphere is dominant for speech in only 70%.

Bilateral representation occurs in 15% of left-handed people, and right-hemisphere language representation occurs in 15% of left-handed people. The primary motor and sensory cortex have been mapped extensively through intraoperative stimulation in awake patients. Early work performed by neurosurgeon Wilder Penfield in Montreal led to the conceptualization of the homunculus, which is the somatotopic representation of the body in both the primary motor and primary sensory cortex (see the image below). Homunculus is somatotopic representation of human body in primary motor and sensory cortex. Some body parts are disproportionately represented because there are more motor and sensory fibers devoted to regions such as face and fingers. View Media Gallery The primary motor cortex corresponds with the precentral gyrus, or Brodmann area 4. Intraoperative stimulation of the motor cortex in awake patients leads to contralateral muscle contraction in a single muscle or discrete group of muscles. The premotor cortex, which corresponds to Brodmann area 6, is also occupied with movement, but typically more complex movements are elicited by stimulation here. The primary sensory cortex corresponds with the postcentral gyrus, or Brodmann areas 1-3.

The homunculus obtained from awake mapping corresponds to that of the motor cortex. Stimulation in awake patients during surgery typically leads to the subjective sensation of tingling of the corresponding body part on the opposite side of the body. Caudally, the superior parietal lobule, Brodmann areas 5 and 7, represents the secondary sensory cortex, which is felt to subserve multimodal sensory information. The primary visual cortex corresponds to Brodmann area 17 and occupies the occipital pole. It is also termed the striate cortex. The visual cortex is retinotopically organized. Surrounding the primary visual cortex is the visual association cortex, or Brodmann areas 18 and 19. The primary auditory cortex lies on the superior bank of the superior temporal gyrus and corresponds to Brodmann area 41. Like the primary motor, primary sensory, and visual cortices, the primary auditory cortex is tonotopically organized. The auditory association cortex, or Brodmann area 42, surrounds the primary auditory cortex.

Previous An Overview of the Brain - AboutKidsHealth An Overview of the Brain MainPlaceHolderTop MainPlaceHolder The brain is an organ that, together with the spinal cord, forms the central nervous system (CNS). Each part of the brain has a different job. The different parts of the brain are connected to each other in complex networks that control and coordinate everything we do. Here are some examples of functions that the brain controls: movement such as walking or stretching seeing, smelling, touching, tasting, and hearing (the five senses) emotions, thoughts, and memory digesting food talking and understanding The brain is like a busy city. Each part has different functions and is made up of different types of cells. To work, different parts of the brain need to send messages to each other, and to other parts of the body. Read further to find out about the different parts of the brain and what they do, how the brain is organized, and what parts make up the brain. There are three major parts of the brain: the cerebrum, the cerebellum, and the brainstem. The cerebrum The cerebrum is often used as another word for the brain. It is the largest part of the brain and fills most of the upper skull.

The cerebrum uses information from our five senses to help us understand what is happening around us. Then it tells our body how to respond. It also controls our emotions, and our ability to talk, think, read, and learn. The surface of the cerebrum is called the cerebral cortex or “grey matter.” Underneath the surface is the “white matter” and deeper structures: the basal ganglia and the limbic system. Cerebral Hemispheres -UNIQUE1-Cerebral_hemispheres_MED_ILL_EN-UNIQUE2- The left cerebral hemisphere controls the right side of the body. The right cerebral hemisphere controls the left side of the body. The cerebral cortex is divided into the right and left cerebral hemispheres. In most people, the two hemispheres perform distinct functions: The left hemisphere plays an important role in language, verbal memory, reading, writing, and arithmetic. It is concerned with sensation and movement on the right side of the body. The right hemisphere plays a large part in interpreting what we see and touch, and in non-verbal memory, music, and emotions. It is concerned with sensation and movement on the left side of the body.

The left hemisphere dominates language in almost all right-handed people and in many left-handed people. In some people, though, the two hemispheres share the language function more equally, and in a few people the right hemisphere may be dominant for language function. The left and right cerebral hemispheres are connected by a bundle of nerve fibres called the corpus callosum, which allows the two cerebral hemispheres to communicate. Each hemisphere is divided into lobes: frontal, temporal, parietal, and occipital lobes. The frontal lobes are large, complex structures. They contain the motor cortex, which controls movement, and are important for speech, planning, problem solving, social and emotional behaviour, self-awareness, and self-control. The occipital lobes contain the primary vision centres as well as areas that help us visually recognize objects and understand what written words mean. The temporal lobes are the main area responsible for memory about facts and events. Together with the limbic system, they help us express emotions and understand the emotions of other people. They seem to have an effect on personality. They are also very important for hearing, and help us understand language and sounds such as music.

The parietal lobes interpret sensations and messages from other parts of the brain. They make connections between the information from all the different senses and store memories. These lobes interpret touch, temperature, pain, sounds, and visual information about objects and the environment. They help us understand shape, size, texture, and direction. These functions often overlap in areas where two lobes meet. For instance, the area where the parietal and temporal lobes meet is responsible for helping us recognize faces. What do the basal ganglia do? The basal ganglia are a group of structures around the thalamus, including the putamen, globus pallidus, and caudate nucleus. The basal ganglia are important for voluntary movement. What does the limbic system do? The limbic system is a complex network of brain areas that includes the amygdala and the hippocampus, as well as the interior parts of the temporal, frontal, and parietal lobes. The limbic system is the “primitive” or “animal” part of our brain. It controls our immediate, automatic responses to stimuli -- our “gut reactions.” The amygdala and hippocampus are located next to the temporal lobes and communicate closely with them.

The amygdala coordinates how emotions affect the autonomic and endocrine systems (for instance, the “fight or flight” response, which causes us to breathe quickly and produce adrenaline in response to fear). The hippocampus is important for storing long-term memories. The cerebellum The cerebellum is located under the cerebrum at the back of the brain. It coordinates our balance and complex movements. For example, actions such as walking or playing the piano are coordinated by the cerebellum. It contributes to the control of speech, and also participates in many of the functions controlled by the cerebrum in ways that are not understood fully. The brainstem The brainstem connects the brain and the spinal cord. It passes messages back and forth between parts of the body and the brain. The brainstem controls functions such as breathing, blood pressure, body temperature, heart rhythms, hunger and thirst, and sleep patterns. It is made of three parts: the midbrain, pons, and medulla oblongata. The midbrain is located between the pons and the cerebral hemispheres. It allows messages to be relayed for sight and hearing, and is also involved in movement.

The pons sends messages between the cerebrum and cerebellum and the spinal cord. The medulla oblongata connects the brain with the spinal cord. Together with the pons, it controls autonomic functions such as breathing and heartbeat. Other structures and nerves are associated with the brainstem. The thalamus and the hypothalamus sit above the brainstem and below the cerebrum. The cranial nerves start in the brainstem and direct many functions, such as smelling and moving our eyes. What does the thalamus do? The thalamus is a structure located on top of the midbrain. All the messages to and from the cerebrum pass through the thalamus. It has a role in feeling pain. What does the hypothalamus do? The hypothalamus is below the thalamus. It helps control appetite, sleeping, body temperature, emotions, and blood pressure. It releases important hormones, which are chemical signals, to the pituitary gland. What does the pituitary gland do? The pituitary gland is attached to the hypothalamus. It receives messages from the hypothalamus. It also releases important hormones, which are chemical signals to other parts of the body.

What are cranial nerves? Cranial Nerves -UNIQUE1-Cranial_nerves_MED_ANI_EN-UNIQUE2- The 12 pairs of cranial nerves connect to the brainstem and the thalamus. Except for the vagus nerve, these nerves send and receive information from the sense organs and muscles of the head, neck, and shoulders. Each nerve has a special role. The nerves and the functions they control are shown in the illustration. The ventricular system and cerebrospinal fluid The brain also contains four fluid-filled structures called ventricles, which make cerebrospinal fluid (CSF). What are ventricles? The ventricular system consists of four fluid-filled spaces in the brain called ventricles. The ventricles are connected by tubes and holes. The choroid plexus is a structure in the ventricles that produces cerebrospinal fluid (CSF). The ventricles are located in the following areas: The first two ventricles are located in the cerebral hemispheres. They are called the lateral ventricles. The third ventricle is in the centre of the brain. The thalamus and hypothalamus make up part of its walls.

The fourth ventricle is behind the brainstem (behind the pons and medulla oblongata), between the brainstem and the cerebellum. The outer layer (or cortex) of the brain is called grey matter, and is made mostly of neuron cell bodies and synapses. White matter is underneath the grey matter, and is made up of long neuronal axons covered by a fatty sheath called myelin. Myelin insulates the axons and facilitates the conduction of electrical impulses. Three layers of tissue called the meninges cover the brain and spinal cord. The brain is also cushioned by CSF. It flows through the ventricles and in the spaces around the meninges. The brain is covered by bones called the cranium. The bones of the cranium, together with other bones that protect the face, form the skull. What is the spinal cord made of? The spinal cord is made up of neurons that connect the brain to most parts of the body. Like the brain, the spinal cord is covered by three layers of tissue called the meninges and cushioned by CSF. It is protected by a bony covering called the vertebral or spinal column. What are the meninges made of?

The meninges are made up of three thin layers of tissue. They are called the dura mater, the arachnoid, and the pia mater. CSF flows in between the arachnoid and pia mater membranes. This area is called the subarachnoid space. What is a neuron? A neuron is a nerve cell that sends and receives messages. It consists of a body, where chemicals called neurotransmitters are produced, and a long axon that connects to other neurons. There are about 100 billion neurons in the human brain. What are neuroglial cells? Neuroglial cells, or neuroglia, protect and support nerve cells. These cells are also called glia or glial cells. Some different types of neuroglial cells are oligodendroglia, astrocytes, and ependymal cells. What is a synapse? A synapse is the gap between neurons. Nerve impulses (messages) travel through the synapse from one neuron to the next by means of chemicals called neurotransmitters. What is a neurotransmitter? A neurotransmitter is a chemical that carries a message from one neuron to the next across a synapse.

If enough neurotransmitter molecules pass from one neuron to the next, they have an effect on that neuron. Some neurotransmitters excite neurons, causing them to fire; others suppress or inhibit them. Examples of neurotransmitters are gamma-aminobutyric acid (GABA), glutamate, neuropeptide Y, and dynorphin. What is an ion channel? Ion channels are proteins in the cell membrane that act as tiny gates or switches to control the flow of specific ions, and therefore electrical current, through the cell. There are different ion channels for sodium, potassium​ , calcium, and chloride ions, and different neurotransmitters switch on different ion channels. Differences in the mix of channels on a cell, the number of channels that are open or closed, and the balance of ions inside and outside the cell all have an effect on cell function and communication from one neuron to the next. How does the brain work? Millions of messages constantly move between different parts of the brain and along the nerves to and from the rest of the body. These messages are tiny electrical impulses that propagate or travel along bundles of nerve fibres and between individual neurons. The impulses move from one neuron to the next by means of neurotransmitters.

A neurotransmitter molecule is released by the first neuron and travels across the synapse. When it connects with a receptor on the second neuron, that neuron receives a message. What the second neuron does next depends on: the type of neurotransmitter: some are excitatory, causing neurons to fire, others are inhibitory, preventing them from firing the type of receptor what the neuron has just been doing If enough neurons are excited or inhibited at the same time, there is an effect. If the neurons are in the part of the brain that controls movement, a body part moves. If they are in a part of the brain that controls emotion, you feel fear or happiness or another emotion. Something as simple as noticing a pencil and picking it up involves many steps: Light bounces off the pencil, into your eye and off your retina. Receptors in the retina fire and send messages along the optic nerve to the occipital lobe of the brain. When the neurons in the occipital lobe get the message, they send further messages to other parts of the brain. These confirm that you are looking at a pencil and not a pen or a mug, decide whether you want it, and figure out how to get it.

The planning areas of the brain send a message to the motor cortex, telling it to reach your hand over to where the pencil is. Neurons in the “hand and arm” section of the motor cortex fire. This sends electrical impulses to the muscles in your arm and hand, which move. When your fingers are touching the pencil, special touch receptors in the skin detect it. They fire, sending yet another message along the nerves to the sensory cortex in the brain. Various areas of the brain figure out whether your fingers are holding the pencil firmly enough and tell the motor cortex to lift your hand, with the pencil in it. Obviously, the brain performs most of these steps without you having to think about it. You are only conscious of seeing the pencil and picking it up -- the whole process may take only a fraction of a second. Reviewed By Elizabeth J. Donner, MD, FRCPC Elizabeth J.

Donner, MD, FRCPC 2/4/2010 How Alcohol Affects the Brain The Cerebral Cortex and Alcohol | The Limbic System and Alcohol | The Cerebellum and Alcohol | The Hypothalamus, Pituitary Gland and Alcohol | The Medulla and Alcohol The cerebral cortex and alcohol The cerebral cortex processes information from your senses, processes thoughts, initiates the majority of voluntary muscle movements and has some control over lower-order brain centers. In the cerebral cortex, alcohol can: Affect thought processes, leading to potentially poor judgement. Depresses inhibition, leading one to become more talkative and more confident. Blunts the senses and increases the threshold for pain. As the BAC increases, these effects get more pronounced. The limbic system and alcohol The limbic system, which consists of the hippocampus and septal area of the brain, controls memory and emotions. The affect of alcohol on this sytem is that the person may experience some memory loss and may have exaggerated states of emotion. The cerebellum and alcohol The cerebellum coordinates muscle movement. The cerebral cortex initiates the muscular movement by sending a signal through the medulla and spinal cord to the muscles.

As the nerve signals pass through the medulla, they are influenced by nerve impulses from the cerebellum, which controls the fine movements, including those necessary for balance. When alcohol affects the cerebellum, muscle movements become uncoordinated. The hypothalamus, pituitary gland and alcohol The hypothalamus controls and influences many automatic functions of the brain (through the medulla), and coordinates hormonal release (through the pituitary gland). Alcohol depresses nerve centers in the hypothalamus that control sexual arousal and performance. With increased alcohol consumption, sexual desire increases - but sexual performance declines. By inhibiting the pituitary secretion of anti-diuretic hormone (ADH), alcohol also affects urine excretion. ADH acts on the kidney to reabsorb water, so when it is inhibitted, ADH levels drop, the kidneys don't reabsorb as much water and the kidneys produce more urine. The medulla and alcohol The medulla (brain stem) influences or controls body functions that occur automatically, such as your heart rate, temperature and breathing. When alcohol affects the medulla, a person will start to feel sleepy. Increased consumption can lead to unconscious.

Needless to say, alcohol's effect on the medulla can be fatal if it is excessive. Menu

Question: Where in the body are the cerebellum, the medulla and the hypothalamus?
Answer: Brain